There is a multi-RAT user equipment (UE) having capability in which the multi-RAT UE can access two or more radio access technologies (RATs). In order to access a specific RAT, connection to a specific RAT can be established on the basis of a UE request, and data transmission/reception can be achieved on the basis of the UE request.
However, although the multi-RAT UE has the capability to access two or more RATs, the multi-RAT UE cannot simultaneously access multiple RATs. In other words, although a current UE has multi-RAT capability, the UE cannot simultaneously transmit and receive data through different RATs.
The conventional multi-RAT technology need not perform interworking between a WLAN and a cellular network, such that overall system efficiency is low. However, a method for solving such low system efficiency has not yet been researched and discussed.